1. Field of the Invention
The present invention relates generally to a V belt for power transmission for use such as in a stepless speed change gear for vehicles. More particularly, the present invention relates to a V belt for power transmission of a type including a looped metallic belt, a plurality of V-shaped metallic blocks arranged in a continuous manner along the length of the metallic belt and each fitted at a radially outer concave groove thereof on the metallic belt, from inside in the radial direction, to be brought into engagement with the V-shaped grooves of driving and driven V-pulleys, and a plurality of stoppers each fitted from outside in the radial direction of the metallic belt on one of the V-shaped blocks, to secure the block to the metallic belt, respectively.
2. Description of Relevant Art
Recently, as a V belt for power transmission for use such as in a stepless speed change gear for vehicles, there have been proposed V belts for power transmission which include a looped metallic belt, a plurality of V-shaped metallic blocks arranged in a continuous manner along the length of the metallic belt and each fitted at a radially outer concave groove thereof on the metallic belt, from inside in the radial direction, and a plurality of stoppers each fitted from outside in the radial direction of the metallic belt on one of the V-shaped blocks, to secure the block to the metallic belt, respectively. In applications in which such type of V belt is stretched over driving and driven V-pulleys, the V-shaped blocks conveniently engage, as they come into contact, with the V-shaped grooves of the V-pulleys.
As an example, there is a V belt disclosed in a utility model application of the present applicant, laid open June 1, 1985 by Japanese Utility Model Application Laying-Open Gazette No. 60-79038. This V belt further includes a plurality of cylindrical rollers each respectively intervening between neighboring two of the V-shaped blocks. These blocks are each formed at the front and rear faces thereof in respect of the advance direction of the V belt with a pair of oppositely arranged semi-cylindrical concave places for receiving to hold corresponding two of the rollers, respectively. Each roller has its axis oriented in the width direction of the V belt.
The V-shaped blocks and the stoppers of this V belt are all configured as illustrated in FIGS. 13 and 14A of the accompanying drawings, respectively. As shown in FIG. 13, each V-shaped block 403 has a concave groove 403a formed in the radially outer part thereof to be fitted on the metallic belt, from inside in the radial direction, one of the semi-cylindrical concave places 403c at the front part thereof to receive a corresponding one of the rollers as well as the other (not shown) of same at the rear part thereof, and a pair of substantially L-shaped grooves 403b, 403b in the left and right shoulder parts thereof, respectively, to secure a corresponding one of the stoppers. In the L-shaped grooves 403b, 403b, left and right L-shaped parts 405b, 405b of the stopper 405 made of a round bar material as shown in FIG. 14A are inserted to be fixed. The L-shaped parts 405b, 405b have their end parts 405d, 405d bent to be outwardly oriented in the radial direction of the V belt, when fixed. A widthwise intermediate part 405c of a bridging base portion 405a of stopper 405 is curved in either sense of the length direction of the V belt, to thereby provide a resilient nature. It thus easy to make the stopper 405 resiliently deform at the base portion 405a to open in a uniform manner in such longitudinal directions of the V belt as shown by arrows X in FIG. 14A. It is, however, relatively difficult to resiliently deform the stopper 405 such that it is uniformly opened with the L-shaped parts 405b, 405b spread in lateral directions of V-shaped block 403. Moreover, the stopper 405 with the L-shaped parts 405b, 405b is rather complicated in configuration. As a result, a straight-forward application of stopper 405 to V-shaped block 403 from outside in the radial direction has been difficult.
For a stopper 505 with such a configuration as shown in FIG. 14B, its application to the V-shaped block 403 would be possible from ahead thereof, without its having to be laterally opened with the L-shaped parts 505b, 505b spread. In this respect, the stopper 405 of FIG. 14A has the bent parts 405d, 405d which constitute an obstacle, whereby its insertion into the L-shaped grooves 403b, 403b of V-shaped block 403 is difficult to be made from ahead without laterally opening same. The stopper 505 of FIG. 14B may be made of a round bar material. Also, its base portion 505a has a widthwise intermediate part 505c thereof curved in the length direction of the V belt, if applied. Thus, it would still be difficult to make the stopper 505 uniformly open in a resilient manner with the L-shaped parts 505b, 505b spread in lateral directions of the V-shaped block 403. Moreover, the application of stopper 505 from ahead to V-shaped block 403 would require two steps such that the stopper 505 should be inwardly brought in place from outside in the radial direction of the V belt before it is inserted into the L-shaped grooves 403b, 403b by its translation in the length direction of the V belt. It would thus be difficult to make a concurrent multiple application of a plurality of stoppers 505 to a plurality of V-shaped blocks 403 which are arranged adjacent to each other along the metallic belt. As a result, the fabrication process may be complicated. Further, because the stopper 505 lacks bent end parts. Such as parts 405d, it would always have associated therewith the unfavorable possibility of coming out of place while the V belt is running. This is true even if it was designed to be clamped on the V-shaped block 403 as firmly as possible. Accordingly, there is a desideratrum to be achieved to possibly facilitate the application of a stopper to a V-shaped block, preferably in a multiplicable manner. More generally, a facilitation in assembly work of V belts is desired.
The present applicant has disclosed, in a utility model application laid open July 10, 1985 by Japanese Utility Model Application Laying-Open Gazette No. 60-101245, a V belt for power transmission of a type similar to that according to the Laying-Open Gazette No. 60-79038, though the former includes a stopper held between shoulder parts of a V-shaped block. This stopper also has a widthwise intermediate part of a base portion thereof curved in the length direction of the V belt. Thus, also the V belt according to the Laying-Open Gazette No. 60-101245 has like problems on assembly work to that according to the Laying-Open Gazette No. 60-79038.
Incidentally, in such a type of V belt for power transmission as proposed in the aforementioned Gazettes, for a given length of a looped metallic belt with given numbers of V-shaped blocks and rollers, the blocks and rollers in a loop have a total play in dependence on the summation of the outside diameter of the respective rollers and the summation of the distance between the deepest part of a front concave place and that of a rear concave place (hereinafter called "minimum longitudinal thickness") of the respective blocks. The tension of the metallic belt depends on this play. Exemplarily, the metallic belt has a greater tension as the play becomes smaller. The total play is required to have a predetermined value, of which the setting is possible by adjusting the outside diameter of the rollers and the minimum longitudinal thickness of the blocks. In this respect, the V belt according to the Laying-Open Gazette No. 60-101245 uses V-shaped blocks of a kind having a predetermined minimum longitudinal thickness and rollers of three different outside diameters to obtain a proper play. More particularly, the rollers are sized into three groups: one including standard rollers having a predetermined standard outside diameter, and the remaining two including rollers smaller and larger by 0.1 mm (for example) in outside diameter than the standard rollers, respectively. Those rollers are designed for a mass production at low cost with a manufacturing tolerance of outside diameter within approximately two microns.
In the described type of V belt, the metallic belt has an increased length with time of use of the V belt, depending on its metallurgical properties. However, the outside diameter of the rollers as well as the minimum longitudinal thickness of the V-shaped blocks is almost unchanged with the time of use of V belt. As a result, the total play of the looped blocks and rollers increases, thus causing the tension of the metallic belt to be reduced from an initially set value. Using a V belt of such state may provide a power transmission gear, a stepless speed change gear for vehicles in this case, with a tendency to malfunction or produce noises. It thus becomes necessary to disassemble such V belt to adjust the total play of block-and-roller loop and then reassemble same.
The disassembly and reassembly work may follow various known methods, which are all complicated. For example, in the case of the V belt according to the Laying-Open Gazette No. 60-101245, the standard rollers are to be replaced, some with rollers smaller by 0.1 mm in outside diameter and some with rollers having a 0.1 mm larger outside diameter. Such practice requires the respective rollers to be measured for outside diameter one by one after disassembly of the V belt. It is possible to include size indication marks on the rollers and eliminate the measurement step. However, the rollers are smaller than the V-shaped blocks and interposed therebetween, so that even if they had their size indication marks put thereon it would be difficult to visually identify them from outside. For such reasons, there is a desideratum for a facilitation of V belt disassembly and reassembly work in conjunction with necessary repairing for adjusting the total play of a block-and-roller loop which may be increased due to extension of the metallic belt with time of use of the V belt. Like desideratum may well apply to the factory adjustment of the total play of the block-and-roller loop in the initial fabrication of the V belt. Therefore, from such point of view as well, a facilitation in assembly work of the V belt is desired.
With such desiderata in mind, the present invention has been achieved to the problems and disadvantages associated with give an effective solution to conventional V belts for power transmission.